provide default value for member variable

Author: kpedro88

SimDataFormats/Track/interface/SimTrack.h

@@ -78,7 +78,7 @@ class SimTrack : public CoreSimTrack {
   math::XYZVectorD tkposition;
   math::XYZTLorentzVectorD tkmomentum;
 
-  int idAtBoundary_;
+  int idAtBoundary_{-1};
   math::XYZTLorentzVectorF positionAtBoundary_;
   math::XYZTLorentzVectorF momentumAtBoundary_;
   uint8_t trackInfo_;